(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly, to a method for improved and increased removal of residue created during and as a result of the process of polishing a copper surface.
(2) Description of the Prior Art
One of the critical parameters that must be maintained during the creation of a semiconductor device is the planarity of surfaces that form part of the created semiconductor device. A number of different methods can be used to achieve and maintain surface planarity, of these methods the process of Chemical Mechanical Polishing (CMP) has become a leading method of planarization for advanced, high-performance Integrated Circuit (IC) devices.
One of the methods that have in addition been applied for the improvement of device performance is to use methods of interconnect that result in low resistive loss over lines of interconnect of the devices. This has led to the introduction of copper as an interconnect medium, whereby in addition and for reasons of production efficiencies, a damascene or dual damascene process is frequently applied for the creation of such interconnects. This leads to the situation whereby requirements of copper polishing, using methods of CMP, are one of the more critical processing steps, particularly applied during the backend creation of interconnect metal comprising copper. As a result, the process of planarizing copper surfaces has the potential of becoming a major yield detractor in creating semiconductor devices. This leads to the need for providing a method of polishing copper surfaces that is readily integratable into a manufacturing process and that has no or a minimum impact on production yield.
One of the sources that have been identified as being a cause of problems encountered during polishing of copper surfaces is the residue of semiconductor materials in the slurry that is used as part of the process of CMP. This residue can for instance be created by un-dissolved chemicals, metals and the like. A common practice to reduce the presence of polishing slurry and the therein contained and undesirably residue is the application of a step of thoroughly rinsing a polished surface with DI water (DIW). This step however adds relative complexity and therewith cost to the process of creating semiconductor devices. It is therefore desirable to provide a method of polishing metal surfaces, preferably comprising copper, such that the polishing process meets requirements of surface planarity, cost, yield and throughput. The invention addresses these concerns and provides such a method.
U.S. Pat. No. 6,328,042 B1 (Gotkis) shows a method to remove residue post copper chemical-mechanical polish.
U.S. Pat. No. 6,234,870 B1 (Uzoh et al.) shows an electro-chemical mechanical wafer processor including heads and rinses.
U.S. Pat. No. 6,2676,996 (Chopra) shows a copper CMP process.
U.S. Pat. No. 6,274,478 B1 (Farkas) reveals a copper CMP process.
A principle objective of the invention is to provide an improved method of polishing copper surfaces.
Another objective of the invention is to provide an improved method of slurry removal during the process of polishing a copper surface.
Yet another objective of the invention is to decrease a negative yield impact that is potentially introduced as a result of polishing a copper surface.
A still further objective of the invention is to provide a method of polishing the surface of a layer of copper that is cost-effective and that is readily integratable into a conventional processing stream of creating semiconductor devices.
In accordance with the objectives of the invention a new method and sequence is provided for the polishing of the surface of a layer of metal containing copper. One of the main problems that are conventionally encountered during the polishing of a copper surface is insufficient removal of the slurry and the therein contained residue of semiconductor materials. The invention therefore provides for an improved method of residue removal. Using the conventional step of applying DIW, the contact between the polishing pad and the surface that is being polished is constant and uninterrupted during the step of applying DIW. The invention improves the removal of slurry as part of the step of applying DIW by, during the step of applying DIW, raising the wafer carrier, thus allowing uninhibited removal of the slurry from the surface that is being polished. After the wafer carrier with the thereon contained wafer has been raised and thoroughly cleaned, the wafer carrier is again lowered, bringing the wafer in renewed contact with the polishing pad and allowing for the polishing of the copper comprising surface to proceed. The step of raising the wafer carrier may be repeated a number of times for further and additional removal of slurry from the interface between the wafer that is being polished and the polishing pad.